Yeah, I concur, El Capitan was the last for me using FCP 7. I keep it installed on the model 4,1 8-core tower
I've had for a decade, to handle old FCP client projects I don't want to transfer over to FCP 8.

FCP 8 (AKA Premiere Pro CC) works fine under High Sierra (10.13) but watch out, 32 bit Quicktime ends when you install Mojave! All 32 bit media will need to be transcoded to work in the 640bit world.

Joe Riggs:
Come OSX Mojave, the jig is up for FCP7. FCP7 worked increasingly poorly in the operating systems after Lion, and couldn't run at all in OSX High Sierra, but you had the option of making your computer dual bootable. That way FCP7 runs happily in an earlier operating system in a bootable volume of its own, and FCP7 in that volume and your newer software in your up-to-date bootable volume, can exchange files. I run FCP7 in Lion and Mountain Lion volumes, while jumping to a Sierra volume to run other software. Occasional reboots become a part of life.

Mojave breaks this happiness by practically demanding that it run in the APFS file system. The pre-High Sierra operating systems run in the HFS+ file system and can't write to APFS.

You might as well use two computers, for the old and the new, and pass data back and forth with an HFS+ formatted portable hard drive.

Loren, your report is baffling. "32-bit" and "64-bit" pertain to operating systems, and programs, not to media files. When you say "32 bit Quicktime", do you mean the old QuickTime (Pro) program 7.6.6 on which FCP7 leaned, or do you mean QuickTime media files, namely .mov files?

Now a .mov video file does specify a codec, and a codec requires a decoder to play the video, and that decoder is a program which can be 32-bit or 64-bit and may or may not be operational under one or another operating system. One can imagine codecs for which there are only decoders (and encoders) that Mojave can't handle, or that only Mojave can handle. I'd be shocked if any video .mov file in any common codec couldn't be used with Mojave. Yet you say old media files need to be transcoded for Mojave. "Transcoded" means transformed to a new codec, and for lossy codecs this would imply increased loss. Unacceptable!

Please clarify what exactly Mojave does to what. I am avoiding the post-Sierra operating systems because their requiring APFS disk format ruins what is to me the main advantage of Macs: its easy multibootability. Perhaps your alarm really revolves around the new file system.

I get most my obsolescence info from Larry Jordan's "Edit Well" site. I recall he's informed readers that coming with Mojave and later, Quicktime 7 .mov's simply won't work under the new media foundations, which are 64 bit. If not Mojave, then Carolina will lower the boom. And even now, under High Sierra, I find when bringing over many older QT7 videos, they simply don't play- some can be saved out as converted files in QuickTime X in order to play. Others will not convert! So I'm curious to know what the secret sauce is to make them work in modern 64-bit space.
I have hundreds of older media captures, I'm looking for a good cheap batch transcoder. Maybe ClipWrap? Compressor?

Hi Loren,
I'm curious about this, and like you, anxious about becoming obsolete while still going.
.mov is a container file format. An encoded video slips into it. We should check if the new Mac software is just griping about the container, or about the encoding within it. I suggest you find a rejected .mov file, and use MPEG Streamclip to save it as an .mp4. It's practically the same container file format, but not Mac-fussy. The encoding isn't touched in the save-as, which takes an instant. Then see if the new Mac software rejects the .mp4 file.

It's always possible that new software does not recognize an old codec and that there's no way to install it in the new software's repertoire. That's normal progress, part of video.

I'm just now wondering how best to archive many old videos. They're all .mov files and in many codecs. I'm inclining toward making DCPs from each. DCP has the advantage of being strictly frame-by-frame. Also its display colors are strictly determinate -- finally a video that you're sure of how it will look. It's so popular a format that it should last a while.

Dennis Couzin
Berlin, Germany

[note added 24 June 2019: The information Loren referred to is at [larryjordan.com] .]